This invention relates to an improvement in air brakes of the type wherein a caliper moves a brake shoe against the outboard side of a rotor while, concurrently, a piston moves a brake shoe against the inboard side of the rotor, and, the caliper moves on upper and lower slide pins, and, the caliper supports an air chamber. Such air brakes are exemplified by Rockwell DURA-MASTER .RTM. Air Disc Brakes as described in Field Maintenance Manual No. 4M of Automotive Operations, Rockwell International Corporation, 2135 West Maple Road, Troy, Mich. 48084, the revision of 4-87.
A persistent problem with this type of air brake has been excessive wear on the outboard brake lining and the outboard surface of the rotor, caused by failure of the caliper to retract upon brake release. The cause of this failure to retract has been attributed to the caliper binding on the slide pins.
Attempts to resolve the problem have been numerous. One attempted solution to the problem involved a change in the slide pin bushings where a split bushing was changed to a one-piece press-in bushing with no apparent improvement.
Another attempted solution was a redesigned slide pin. This design introduced on "O" ring in a groove on the slide pin to provide a buffer area between the caliper bushings and the slide pin to eliminate binding. This change exacerbated the problem.
A more recent attempt at solving the problem included enlarging the inside diameter of the bushing, and the introduction of a larger "O" ring on the slide pins and the addition of an accelerator valve. This made the problem even worse.
The problem of failure of the caliper to retract with consequent excessive wear on the caliper and outboard face of the rotor and the efforts to resolve the problem have persisted for more than 10 years with no workable solution prior to the present invention, which reduces the frictional forces on the guide pins by suspending a portion of the weight of the air chamber from the upper slide pin while providing a component of force opposite to the direction of movement of the caliper when the caliper produces a braking force on the outboard surface of the rotor.
It is, therefore, an object of this invention to reduce wear in the break lining of the caliper in a brake of the type described.
A concurrent object of this invention to reduce wear on the outboard surface of the brake rotor in such brakes.
It is further object of this invention to reduce downtime and maintenance costs in these brakes.
It is a still further object of this invention to achieve the foregoing objects by a simple and economical method of retrofitting existing brakes.